[transmission mechanism of sheet feeder]

ABSTRACT

A transmission mechanism comprising three drive rollers, one idle roller, one belt, and an elastic member. The belt is tightened around the drive rollers, where they drive the belt to rotate. The elastic member activates the idle roller causing the idle roller to exert a force on the belt for moving a document between the idle roller and belt during transportation of the document.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of Taiwanapplication serial no. 91119633, filed Aug. 29, 2002.

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is generally related to the transmissionmechanism of a sheet feeder, and particularly, to the transmissionmechanism of a shrunk-size sheet feeder.

[0004] 2. Description of Related Art

[0005] Following the advancement and rapid development in theelectronics industry, it has risen to become the most important industryof our current society. A variety of different processing systems areintroduced therefore leading to the popularization of electronicproducts in our daily lives. In the recent years, the processing speedand storage capability of CPUs and personal computers have greatlyincreased. As a result, the efficiency of image processing is greatlyenhanced allowing consumers to enjoy image-processing devices such asoptical scanners and digital cameras.

[0006] The different categories of image document inputs are opticalpocket scanner, sheet feed scanner, drum scanner, and flatbed scanner,or the like. Sheet feed scanners are geared towards lighter, thinner,shorter, and smaller, and therefore the feed mechanism of the sheet feedscanner has to be correspondingly reduce in size.

[0007] Please refer to FIG. 1, a schematic diagram of a conventionalsheet feeder is shown. The sheet feeder 110 is used for feeding adocument 150 and the sheet feeder 110 comprises of a sheet feeder body162, a feed-in tray 112, a feed-out tray 128, three drive rollers 114,three idle rollers 118, a separate roller 126, a feed roller 122, and aseparate plate 124. Feed roller 122 is located inside the sheet feeder110 at one end of the feed-in tray 112. The drive rollers 114 and idlerollers 118 are located inside the sheet feeder 110, where the driveroller 114 and idle roller 118 are grouped together to transport adocument 150 by having a pair of drive roller 114 and idle roller 118 tomake contact with different faces of the document 150. The separateroller 126 and the separate plate 124 are both located inside the sheetfeeder 110, wherein the separate roller 126 is placed above the separateplate 124 and they are both in contact. The material of the separateroller 126 is a flexible material, therefore when a stack of sheetspasses through the separate roller 126 and the separate plate 124 theseparate roller will only allow one piece of paper to pass through underideal situation. This is due to the friction between the separate roller126 and the to-be-fed sheet is greater than that between sheets andbetween the sheet and the separate plate 124.

[0008] Feed roller 122 feeds a document 150 in a first direction 120towards the passage created between the separate roller 126 and theseparate plate 124 and by combining the design of the separate roller126, the separate roller 126 and the separate plate 124 will only allowone document 150 to pass through at each time. After passing through thepassageway between the separate roller 126 and separate 124 plate, thedocument 150 will be fed in a second direction 140 towards the passagebetween the drive roller 114 and the idle roller 118. The drive roller114 and the idle roller 118 together clamp both sides of the document150 and then feed in a third direction 160. When the document 150 is atthe scan entrance 116, the document 150 is fed through the scan entrance116 in the third direction 160 until the scanner 132 has finishedscanning the image of the document 150 and the drive rollers 114 exitsthe document to the feed-out tray 128.

[0009] In the above-described sheet feeder 110, the drive rollers 114,the idle rollers 118, the separate roller 126, the feed roller 122, andthe separate plate 124, etc. . . of the sheet feeder 110 all occupysignificant space inside the sheet feeder 110. Therefore the sheetfeeder 110 requires a relatively large volume to accommodate all thesecomponents. Furthermore, the conventional sheet feeder 110 relies onpairs of drive rollers 114 and idle rollers 118 to feed a document 150.The drive rollers and idle rollers 118 use a point-contact method tofeed documents, which easily causes slippage of document 150 thataffects the quality of the scan.

[0010] An object of the present invention is to provide a transmissionmechanism which reduces the total number of rollers to reduce the spaceoccupied by the rollers and furthermore to effectively shrink the sizeof the sheet feeder.

[0011] Another object of the present invention is to provide atransmission mechanism which uses face-contact method to feed documents,which feeds in accurately for scanning to improve scan quality.

SUMMARY OF INVENTION

[0012] In order to achieve the above objects, the present inventionprovides a transmission mechanism comprising three drive rollers, a idleroller, a belt, and an elastic member. The belt tightens around thedrive rollers to drive all of drive rollers simultaneously. The elasticmember activates the idle roller causing the idle roller to exert aforce on the belt to move the document between the idle roller and beltduring transportation. This setup can reduce the total number of rollers(including drive rollers and idle rollers) to reduce the size occupiedby the rollers for effectively reducing the size of the sheet feeder.The elastic member exerts an elastic force, which is tangent to thedocument and the idle roller, on the idle roller to generate a frictionbetween the belt and the document in order to move the document. Theelasticity of the elastic member can adjust the distance between thebelt and idle roller so the transmission mechanism can accommodatedocuments that are relatively thick. Furthermore, the contact betweenthe belt and idle roller is a face-to-face method to transport thedocument so the surface friction between the belt and document isgreater than that between the idle roller and document. As a result thetransportation of the document is more accurate. The elasticity of theelastic member will push the idle roller towards the belt so slacking ofthe belt will be tightened to resume normal operation of thetransmission mechanism.

[0013] In accordance to the above, the present invention reduces thetotal number of rollers (including drive rollers and idle rollers) toreduce the space occupied by the rollers for effectively reducing theoverall size of the sheet feeder. The transmission mechanism uses aface-contact method to transport documents so that the document and beltcan have direct face contact for a more accurate delivery.

[0014] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

[0016]FIG. 1 is a schematic diagram of a conventional sheet feedscanner.

[0017]FIG. 2 is a schematic diagram of the sheet feed scanner accordingto one preferred embodiment of the present invention.

[0018]FIG. 3 is schematic diagram the transmission mechanism of thesheet feed scanner according to one preferred embodiment of the presentinvention.

[0019]FIG. 3A is the top view of the transmission mechanism illustratedin FIG. 3.

[0020]FIG. 3B is a schematic diagram illustrating the relationshipbetween the belt, idle roller, elastic member, and document of FIG. 3.

[0021]FIG. 3C is a schematic diagram illustrating a tightened belt inthe relationship between the belt, idle roller, elastic member, anddocument of FIG. 3.

[0022]FIG. 3D is a schematic diagram illustrating a slacked belt in therelationship between the belt, idle roller, elastic member, and documentof FIG. 3.

DETAILED DESCRIPTION

[0023] Please refer to FIG. 2. FIG. 2 shows the schematic diagram of thesheet feed scanner according to one preferred embodiment of the presentinvention. The sheet feeder 210 comprises of a body 262, a feed-out tray213, a feed-in tray 212, a feed-in roller 222, a feed-out roller 228,and a transmission mechanism 300. The feed-in tray 212 and feed-out tray213 are located outside the body 262 where the feed-in tray 212 islocated above the feed-out tray 213. The feed-in roller 222, feed-outroller 228, and transmission mechanism 300 are all located inside body262. The feed-in roller 222 is disposed at one end of the feed-in tray212 and the feed-out roller 228 is disposed at one end of the feed-outtray 213. The transmission mechanism 300 is located at a side of thefeed-in roller 222 and feed-out roller 228. Furthermore, the sheetfeeder 210 has a scan entrance 216 located directly below the sheetfeeder 210. The scan module 232 receives the document 250 by the sheetfeeder 210 through the scan entrance 216 of sheet feeder 210. Thedocument 250 will be automatically transported through scan entrance 216allowing the scan module to perform a scan of the image of the document250. After scanning of the document 250 by the scan module 232, thedocument will be transported to the feed-out tray 213. In this preferredembodiment, the document 250 is a piece of paper.

[0024] Please simultaneously refer to FIG. 3 and FIG. 3A. FIG. 3 is aschematic diagram of the transmission mechanism and FIG. 3A is the topview of the transmission mechanism according to the preferred embodimentof the present invention. The transmission mechanism 300 comprises ofthree drive rollers 214, a idle roller 226, a belt 229, and an elasticmember 227. Each drive roller 214 further comprises an axle 218, whichpenetrates the center of the drive roller 214 and has its two ends fixedon the body 262. The drive rollers 214 revolves about the axle 218,whereby at least one of the drive rollers 214 must provide a drivingmotion to drive belt 229 and other passive drive rollers 214. Thearrangement of the three drive rollers 214 forms a substantiallytriangular shape with the drive rollers 214 at the three edges. Thetriangular shape can be an acute triangle, right-angle triangle, orobtuse triangle. The number of rollers 214 of the present invention isnot limited to only 3 as shown in the preferred embodiment but can beany other integer number of rollers. The belt 229 tightens around thedrive rollers 214. The belt 229 can be multiple pieces of belt tightenedaround drive rollers 214. The idle roller 226 further comprises a shaft219 which penetrates the center of the idle roller 226 and has its twoends fixed on the body 262. The idle roller 226 revolves about the shaft219. One end of the elastic member 227 is fixed on the shaft 219 and theother end of the elastic member 227 is fixed on the body 262. Theelastic member 227 is a spring in this preferred embodiment andfurthermore can be manufactured as a whole with the body 262 byinjection molding. The body of elastic member 227 possesses elasticitywhich allows the idle roller 226 to be pressed against the belt 229 tomaintain a certain tightness of the belt 229. In effect of the above,the transmission mechanism 300 reduces the total number of rollers(including drive rollers and idle rollers) to reduce the size occupiedby them for reducing the overall size of the sheet feeder 210.

[0025] Please simultaneously refer to FIG. 2, FIG. 3, and FIG. 3B. FIG.2 is a schematic diagram of the sheet feed scanner, FIG. 3 is aschematic diagram of the transmission mechanism, and FIG. 3A and FIG. 3Bis a schematic diagram showing the relationship between the belt, idleroller, elastic member, and document according to the preferredembodiment of the present invention. The transmission mechanism uses amotor (not illustrated) for providing a driving source to one of thedrive rollers 214 to turn feed-in roller 222 and feed-out roller 228 forfeeding a document 250 in the feed-in tray 212 towards a firsttranslation direction 220, whereas the document is a piece of paper.After passing the feed-in roller 222, the document 250 is moved towardsthe passageway between the idle roller 226 and belt 229. The driverollers 214 rotate in a first rotation direction 301 to drive the belt229, and the belt 229 drives the idle roller 226 in a second rotationdirection 302. As a result the document 250 passing through thepassageway between the belt 229 and idle roller 226 is fed in a secondtranslation direction 240. As illustrated in FIG. 3B, the document 250causes the idle roller to move to the right resulting in a tangent forceon the document 250 by the idle roller 226. Therefore a friction isgenerated between the document 250 and belt 229 for transporting thedocument 250 forward to pass through the passageway between the belt 229and idle roller 226 towards a third translation direction 260. Thecontact between the belt 229 and document 250 is a face-contact method,whereas the contact surface friction between the belt 229 and document250 is greater than that between the idle roller 226 and document 250.Furthermore, the elasticity of the elastic member 227 can adjust thedistance between the idle roller 226 and document 250 to accommodatedocuments of different thickness.

[0026] Please simultaneously refer to FIG. 3C and FIG. 3D. FIG. 3C showsa schematic diagram of the relationship of the tightened belt, idleroller, and elastic member of FIG. 3. FIG. 3D shows a schematic diagramof the relationship of the slacked belt, idle roller, and elastic memberof FIG. 3. When transmission mechanism 300 is in normal operation andbefore the belt 229 becomes slack, the contact between the belt and theidle roller 226 is balanced. At this instant, the distance of theelastic member 227 from the center of the shaft 229 to the body 262 is afirst distance of 30, as shown in FIG. 3C. After long operation of thebelt 229, slacking will occur in belt 229 but it is compensated by theelasticity of the elastic member 227 by pushing the idle roller 226towards the belt 229 until the belt 226 and belt 229 maintain a balance.At this moment, the distance of the elastic member 227 from the centerof the shaft 229 to the body 262 becomes a second distance of 40,wherein the second distance 40 is greater than the first distance 30. Inother words, even after slacking occurs, the elasticity of the elasticmember 227 can retain the belt in a condition without slacking to resumenormal operation of transmission mechanism 300.

[0027] According to the above, the advantage of the present invention isa reduced total number of rollers (including drive rollers and idlerollers) to reduce the space occupied by the rollers for reducing theoverall size of the sheet feeder.

[0028] The second advantage of the present invention is the face-contactmethod used in the transportation for better accuracy of documentfeeding.

[0029] The third advantage of the present invention is that theelasticity of the elastic member can adjust the distance between theidle roller and belt for accommodating documents of different thickness.

[0030] The fourth advantage of the present invention is the slacking ofthe belt can be compensated for resuming normal operation of thetransmission mechanism.

[0031] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure and method ofthe present invention without departing from the scope or spirit of thepresent invention. In view of the foregoing description, it is intendedthat the present invention covers modifications and variations of thisinvention provided they fall within the scope of the following claimsand their equivalents.

1. A transmission mechanism of a sheet feeder located inside a body forfeeding a document, the transmission mechanism comprising at least: aplurality of drive rollers; at least a belt, wherein the belt tightensaround the plurality of drive rollers, and the plurality of driverollers drive the belt; a idle roller; and an elastic member, whereinthe elastic member activates the idle roller causing the idle roller toexert a force on the belt for moving the document between the idleroller and the belt during feeding of the document.
 2. The transmissionmechanism in claim 2, wherein the number of drive rollers is three. 3.The transmission mechanism in claim 1, wherein the plurality of driverollers is arranged in a triangular formation where the drive rollersare located at the corners, the triangular formation is selected from agroup including acute triangles, right-angle triangles, and obtusetriangles.
 4. The transmission mechanism in claim 1, wherein the beltfurther comprising a plurality of belts tightened around the pluralityof drive rollers.
 5. The transmission mechanism in claim 1, wherein atleast one of the plurality of drive rollers is driven by a motor todrive all the plurality of rollers.
 6. The transmission mechanism inclaim 1, wherein the elastic member is a spring.
 7. The transmissionmechanism in claim 1, wherein the elastic member is manufacturedtogether with the body by injection molding.
 8. The transmissionmechanism in claim 7, wherein the elastic member is plastic.
 9. Thetransmission mechanism in claim 1, wherein the plurality of driverollers further comprising a plurality of axles, the axles penetrate acenter of the plurality of drive rollers and two ends of the axles arefixed on the body, and the plurality of drive rollers revolve about theaxles.
 10. The transmission mechanism in claim 1, wherein the idleroller further comprising a shaft, the shaft penetrates a center of theidle roller, and the idle roller revolves about the shaft.
 11. Thetransmission mechanism in claim 1, wherein one end of the elastic memberis fixed on the shaft of the idle roller, and the other end is fixed onthe body.
 12. The transmission mechanism in claim 1, wherein thedocument is a sheet of paper.
 13. The transmission mechanism in claim 1,wherein a contact between the belt and the idle roller is a face typecontact.
 14. The transmission mechanism in claim 13, wherein a surfacecontact friction between the belt and the document is greater than thefriction between the idle roller and the document.
 15. The transmissionmechanism in claim 1 further comprising a feed-in roller, a feed-outroller, a feed-in tray, and a feed-out tray, wherein the feed-in rollerand feed-out roller are located inside the body, the feed-in tray andfeed-out tray are located outside the body, the feed-in roller islocated at one side of the feed-in tray, and the feed-out roller islocated at one side of the feed-out tray.
 16. The transmission mechanismin claim 1, wherein an elasticity of the elastic member moves the idleroller towards the belt in a tangent direction and the document movesthrough between the idle roller and the belt.